1. Field of the Invention
The present invention relates to a liquid crystal displaying method, particularly relates to the displaying method which displays a high-quality moving picture including luminance information and color-difference information on a liquid crystal display, by using easy processing in which software can perform real-time processing.
2. Related Art
In recent years, a liquid crystal display is spread in wider fields such as monitors for personal computers, notebook computers, and televisions. Accordingly, an opportunity for viewing a moving picture by the liquid crystal display is greatly increased. However, in the liquid crystal display, since response speed of the liquid crystal is not sufficiently fast, degradation of image quality such as blurring or residual image occurs in displaying moving picture. Generally, since refresh rate of the liquid crystal display is 60 Hz, in order to correspond to the display of the moving picture, a target is the response speed of less than 16.7 ms. In recent liquid crystal displays, though the binary response speed (in the liquid crystal display of the display with 256-level gray-scale, from 0-level gray-scale to 255-level gray-scale or from 255-level gray-scale to of 0-level gray-scale) is less than 16.7 ms, the response speed between the intermediate gray-scale levels is more than 16.7 ms.
The problem that the response speed between the intermediate gray-scale levels is not sufficient because the general moving picture includes a large quantity of the response between the intermediate gray-scale levels results in the degradation of the image quality, so that it is necessary that the response speed is further improved.
In order to improve the response speed of the liquid crystal display, development of a new liquid crystal material having the fast response speed, improvement of a driving method of the liquid crystal display using the conventional liquid crystal material. For the new liquid crystal material, a smectic ferroelectric liquid crystal and anti-ferroelectric liquid crystal and the like are developed. However, there are many problems which should be solved such as a problem of image sticking caused by effect of spontaneous polarization of the liquid crystal, a problem that orientation of the liquid crystal is easy to be destroyed by pressure, and the like.
On the other hand, for the development of the method increasing the response speed of the liquid crystal by improving the driving method of the liquid crystal display using the conventional liquid crystal material, there is a method that a gray-scale level added a predetermined gray-scale level to a writing gray-scale level is written in the liquid crystal display, when the image which is displayed in the liquid crystal display is changed (refer to 2001 SID International Symposium Digest of Technical Papers/Volume XXXII/ISSN-0001-966X P.488). An outline of operation of the method will be described below.
The response characteristics between the gray-scale levels of the liquid crystal display are previously measured, and the gray-scale level reached after one frame period (generally after 16.7 ms) is obtained. From this result, the writing gray-scale level required for changing a certain gray-scale level to another gray-scale level after one frame period is obtained, and stored as two-dimensional array data. That is to say, in the case of the liquid crystal display with the 256-level gray-scale level, in order to store data between all the gray-scale levels, the 256×256 array data is required. From which gray-scale level to which gray-scale level is examined for every sub-pixel of R, G, and B in each pixel in image information inputted to the liquid crystal display, and the writing gray-scale level for completing the response after one frame period is determined as referring to the array data. Namely, in the case that the image information changes from L0 to L1, L1-level gray-scale is not written in the liquid crystal display, but L1′-level gray-scale which can reach the L1-level gray-scale after one frame period is written in the liquid crystal display, referring to the array data. By adopting this method, any liquid crystal display, in which the response from all the gray-scale levels to 0-level gray-scale and from all the gray-scale levels to 255-level gray-scale (in case of the liquid crystal display with the 256-level gray-scale) is completed within one frame period, can complete the response between almost all the gray-scale levels within one frame period.
FIG. 14 shows a concrete system configuration realizing the driving method of the above-described related art. Input image information and the image information delayed for one frame period by a frame memory part 32 are inputted to a gate array part 36. In the gate array part 36, on the basis of the input image information and the image information delayed for one frame period, address information indicating which data should be referred in an array data holding part 34 storing the above-described array data is outputted to the array data holding part 34. The array data holding part 34 outputs the stored array data to the gate array 36 on the basis of the inputted address information. The gate array part 36 outputs the inputted array data as the emphasized image information to a liquid crystal display 38, and the emphasized image is displayed on the liquid crystal display 38.
In the above-described method, there is no problem in the case that the input image information is image information of three primary colors, however, in the case that the input image information is the image information including luminance information and color-difference information, processing becomes complicated or it is necessary to drastically increase the number of array data. In the case that the input image information is the image information including the luminance information and the color-difference information, in the above-described method, in order to obtain the writing gray-scale level of each pixel, it is necessary that the input image information is transformed once into the image information of three primary colors and then a change in the gray-scale level for each sub-pixel is examined. Since the transformation processing from the luminance information and the color-difference information into the image information of three primary colors is relatively high burden, it is difficult for software to perform it in real-time. In the case that the luminance information and the color-difference information are used directly, the array data according to combination of the luminance information and the color-difference information is required, for example, in the case that the input image information includes one of the luminance information and two of the color-difference information, the two-dimensional array data of 2563×2563 is required. With increasing array data, the memory holding the array data requires to be increased, so that a problem of cost occurs. Moreover, when the method referring to the array data is processed with the software, the array data is held in a main memory and the like of the personal computer. However, for the above-described method such as referring the array data, it is difficult that the input image information is displayed in real-time, because random access to the main memory is the processing of the large burden.